Interruptions in wireless communications

ABSTRACT

Method and apparatus for reception of data units in a device by means of a first protocol and a second protocol are disclosed. A control function of the second protocol is informed of interruption in a control function of the first protocol. In response thereto a reordering timer of the second protocol is considered as having expired, and a state variable of the second protocol is updated to equal with a highest received state variable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/349,216, which is the U.S. National Stage of InternationalApplication No. PCT/EP2011/067136, filed Sep. 30, 2011.

The invention relates to methods and apparatuses for wirelesscommunications and in particular to handling of interruptions, forexample handling of retransmissions and/or other functions at a reset ofa protocol.

A communication system enables communication between two or morecommunication devices such as user terminals, base stations and/or othernodes by providing carriers between the communication devices. In awireless communication system at least a part of communications betweenat least two stations occurs over wireless interfaces. A user can accessa communication system by means of an appropriate communication deviceor terminal. A communication device is provided with an appropriatesignal receiving and transmitting apparatus for enabling communications,for example enabling access to a communication network or communicationsdirectly with other users. The communication device may access a carrierprovided by a station, for example a base station of a cell, andtransmit and/or receive communications on the carrier.

A communication system can be provided with error correctionfunctionality, such as with a possibility of requesting forretransmission of any information that the recipient node did notsuccessfully receive. For example, hybrid automatic repeat request(HARQ) error control mechanism may be used for this purpose. The errorcontrol mechanism can be implemented such that a device which receiveseither a positive or a negative acknowledgement (ACK/NACK) or otherindication from another device of an error free or erroneous receipt oftransmitted data can take appropriate action. Typically this meansresending of a protocol data unit to the receiving device in response toa negative acknowledgement so as to rectify the situation.

A problematic situation may occur when there is an interruption inoperation of a protocol handling the error correction. For example,operation of a protocol entity receiving and/or sending protocol dataunits, causing sending of requests for retransmission, and/or respondingthe requests may be temporarily or permanently interrupted, for examplebecause of reset of the entity. This can cause delays in thecommunications. In accordance with an aspect there is provided a methodfor reception of data units in a device by means of a first protocol anda second protocol, comprising informing a control function of the secondprotocol of interruption in a control function of the first protocol,and in response thereto considering a reordering timer of the secondprotocol as expired and updating a state variable of the second protocolto equal with a highest received state variable.

In accordance with another aspect there is provided an apparatus forhandling reception of data units in a device by means of a firstprotocol and a second protocol, the apparatus comprising at least oneprocessor, and at least one memory including computer program code,wherein the at least one memory and the computer program code areconfigured, with the at least one processor, to provide a controlfunction of the second protocol with an indication of interruption in acontrol function of the first protocol, and in response to theindication consider a reordering timer of the second protocol as expiredand update a state variable of the second protocol to equal with ahighest received state variable.

In accordance with a more specific aspect the interruption comprises areset of the control function of the first protocol at a receiving node.

The first protocol may comprise media access control (MAC) protocol. Thesecond protocol may be a protocol is located above the MAC protocol inthe layered protocol model. The second protocol can comprise radio linkcontrol (RLC) protocol or packet data convergence protocol (PDCP).

The control function of the first protocol can provide hybrid automaticrepeat request (HARQ) functionalities. A higher level protocol mechanismmay be used in some embodiments for retransmission of the data unitsinstead of HARQ.

Information of the interruption may be provided by a media accesscontrol (MAC) protocol or radio resource control RRC protocol entity.

The update can comprise update of a maximum status transmit statevariable to equal the highest received state variable or update of anunacknowledged mode receive state variable to equal an unacknowledgedmode highest received state variable.

A status prohibit timer can be stopped and reset in response toconsideration of the reordering timer as having expired.

Expiry of the reordering timer can be considered as having happened inresponse to the information of interruption even if the timer is notrunning.

It can be determined in response to information of the interruption thatno further retransmissions of protocol data units transmitted so far inaccordance with the first protocol can be expected. In response theretoa status protocol data unit in can be sent accordance with the secondprotocol and/or so far received service data units can be delivered toan upper protocol layer.

A communication device, for example a mobile station, can be configuredto operate in accordance with the various embodiments.

A computer program comprising program code means adapted to perform themethod may also be provided.

Embodiments will now be described in further detail, by way of exampleonly, with reference to the following examples and accompanyingdrawings, in which:

FIG. 1 shows an example of a system wherein below described embodimentsmay be implemented;

FIG. 2 shows an example of a communication device

FIG. 3 shows an example of a layered protocol stack of a device;

FIG. 4 shows an aggregated carrier; and

FIG. 5 shows a method of an embodiment.

In the following certain exemplifying embodiments are explained withreference to a wireless communication system serving devices adapted forwireless communication. Therefore, before explaining in detail theexemplifying embodiments, certain general principles of a wirelesssystem, components thereof, and devices involved in wirelesscommunication are briefly explained with reference to exemplifyingsystem 10 of FIG. 1 device 20 of FIG. 2 and protocol stack of FIG. 3.

A communication device can be used for accessing various services and/orapplications provided via a communication system. In wireless or mobilecommunication systems the access can be provided via a wireless accessinterface between mobile communication devices and an appropriate accesssystem. For example, a communication device may access wirelessly acommunication system via a base station. A base station site can provideone or more cells of a cellular system. A plurality of carriers can beprovided by a cell or a base station. In the example of FIG. 1 a basestation 12 is shown to provide three carriers 1, 2 and 3. Eachcommunication device 20 and base station may have one or more radiochannels open at the same time and may receive signals from more thanone source. It should be appreciated that the number of carriersprovided by a base station may vary over time.

It is noted that at least one of the carriers 1 to 3 may be provided bymeans of another station, for example by a remote radio head. Also, atleast one of the carriers may be provided by a station that is notco-located at base station 12 but could only be controlled by the samecontrol apparatus as the other cells. This possibility is denoted bystation 11 in FIG. 1. For example, block 13 could be used to control atleast one further station The controller of a cell has enoughinformation for all of the aggregated carriers or cells.

A base station site is typically controlled by at least one appropriatecontroller so as to enable operation thereof and management of mobilecommunication devices in communication with the base station. Forexample, a control apparatus may be configured to provide controlfunctions in association with generation, communication andinterpretation of information regarding mobile access, error correctionand retransmissions, handovers, carrier aggregation and/or otheroperations. The control apparatus may also provide various timersdepending on the implementation of the system. The control entity can beinterconnected with other control entities. The control entity may bepart of the base station. In FIG. 1 the controller is shown to beprovided by block 13. The controller apparatus may comprise dataprocessing apparatus 14 comprising at least one memory, at least onedata processing unit and an input/output interface. It shall beunderstood that the control functions may be distributed between aplurality of control units. The controller apparatus for a base stationmay be configured to execute an appropriate software code to provide thecontrol functions as explained below in more detail.

In FIG. 1 the base station 12 is connected to a data network 18 via anappropriate gateway 15. A gateway function between the access system andanother network such as a packet data network may be provided by meansof any appropriate gateway node, for example a packet data gatewayand/or an access gateway. A communication system may thus be provided byone or more interconnect networks and the elements thereof, and one ormore gateway nodes may be provided for interconnecting various networks.

An example of a standardized architecture is known as the long-termevolution (LTE) of the Universal Mobile Telecommunications System (UMTS)radio-access technology. A non-limiting example of access networkarchitectures where the herein described principles may be applied isknown as the Evolved Universal Terrestrial Radio Access Network(E-UTRAN). The LTE and E-UTRAN are standardized by the 3rd GenerationPartnership Project (3GPP). The various development stages of the 3GPPspecifications are referred to as releases. A development of the LTE isoften referred to as LTE-Advanced (LTEA). A non-limiting example of abase station of a cellular system is what is termed as a NodeB orevolved NodeB (eNB) in the vocabulary of the 3GPP specifications.

FIG. 2 shows a schematic, partially sectioned view of a communicationdevice 20 that a user can use for communications. Such a communicationdevice is often referred to as user equipment (UE) or terminal. Thedevice may be mobile or have a generally fixed location. An appropriatecommunication device may be provided by any device capable of sendingand receiving radio signals. Non-limiting examples include a mobilestation (MS) such as a mobile phone or what is known as a ‘smart phone’,a portable computer provided with a wireless interface card or otherwireless interface facility, personal data assistant (PDA) provided withwireless communication capabilities, or any combinations of these or thelike. A communication device may provide, for example, communication ofdata for carrying communications such as voice, electronic mail (email),text message, multimedia, positioning data, other data, and so on. Usersmay thus be offered and provided numerous services via theircommunication devices. Non-limiting examples of these services includetwo-way or multi-way calls, data communication or multimedia services orsimply an access to a data communications network system, such as theInternet.

A communication device is typically provided with at least one dataprocessing entity 23, at least one memory 24 and other possiblecomponents 29 for use in software and hardware aided execution of tasksit is designed to perform, including control of access to andcommunications with base stations and other communication devices. Thedata processing, storage and other relevant control apparatus can beprovided on an appropriate circuit board and/or in chipsets. Thisfeature is denoted by reference 26. The control apparatus may providevarious timers, such as a reordering timer 36 and prohibit timer 38.Operation thereof will be explained below in relevant contexts.

The user may control the operation of the communication device by meansof a suitable user interface such as key pad 22, voice commands, touchsensitive screen or pad, combinations thereof or the like. A display 25,a speaker and a microphone are also typically provided. Furthermore, acommunication device may comprise appropriate connectors (either wiredor wireless) to other devices and/or for connecting externalaccessories, for example hands-free equipment, thereto.

The device 20 may receive and transmit signals 28 via appropriateapparatus for receiving and transmitting signals. In FIG. 2 transceiverapparatus is designated schematically by block 27. The transceiverapparatus is provided with radio capability. The transceiver may beprovided for example by means of a radio part and associated antennaarrangement. The antenna arrangement may be arranged internally orexternally to the mobile device.

Currently in systems such as those based on the LTE, intra-cell handover(HO) is usually performed for reconfigurations where synchronisationmust be ensured between the eNB and the user equipment (UE) in order toavoid any ambiguity on whether the UE uses the old or the newconfiguration. For instance, because transmission time interval (TTI)bundling impacts HARQ (Hybrid Automatic-Repeat-Request) operation, theTTI bundling is usually enabled or disabled through an intra-cellhandover. Similarly, if security keys need to be changed while stayingin the same cell an intra-cell HO can be used. This may be the case forinstance in order to avoid hyper frame number wrap-around (HFN). Fromthe essential operational aspects intra-cell handovers do not differfrom regular handover. A characteristic feature of intra-cell handoveris though that signalling is with a target cell that is at the same timethe source cell. In general it is noted that a “light handover” can beperformed for any kind of intra-cell reconfiguration or intra-eNBserving cell change.

In a handover such as the intra-cell handover media access control (MAC)protocol is reset and radio link control (RLC) and packet dataconvergence protocol (PDCP) are reestablished, security keys are updatedand a random access procedure is performed in the target cell. FIG. 3illustrates LTE protocol stack as provided for a device such as userequipment showing the hierarchical order of protocol layers for theseprotocols. Functionalities according to the protocols are provided byappropriate entities of the control apparatus in a user equipment. Ofthe above protocols media access control (MAC) refers to a datacommunication protocol sub-layer, also known as the medium accesscontrol. MAC is a sublayer of the data link layer specified in theseven-layer OSI model (layer 2), and in the four-layer Transport ControlProtocol/Internet Protocol (TCP/IP) model (layer 1). A medium accesscontroller can be provided for the control of the MAC sublayeroperations. MAC provides addressing and channel access controlmechanisms enabling several devices, e.g. user equipment or otherterminals and/or network nodes to communicate within a multiple accessnetwork that incorporates a shared medium. MAC sub-layer can act as aninterface between a Logical Link Control (LLC) sublayer and thenetwork's physical layer. The MAC layer emulates a full-duplex logicalcommunication channel in a multi-point network. Radio link control (RLC)in turn is a link-layer protocol that is responsible for error recoveryand flow control. RLC protocol layer exists in user equipments and eNband is a part of LTE air interface control and user planes. RLC sublayerprovides functions such as transfer of upper layer protocol data units(PDUs), error correction through automatic repeat request (ARQ) foracknowledged mode (AM) data transfer, concatenation, segmentation andreassembly of RLC service data units (SDUs) for unacknowledged mode (UM)and AM data transfer, re-segmentation of RLC data PDUs for AM datatransfer, in sequence delivery of upper layer PDUs for UM and AM datatransfer, duplicate detection for UM and AM data transfer, protocolerror detection and recovery, RLC SDU discard for UM and AM datatransfer, and RLC re-establishment.

A service data unit (SDU) refers typically to a unit of data that hasbeen passed between protocol layers and that has not been encapsulatedinto a protocol data unit (PDU). A PDU can be understood as data unitthat a protocol passes to/from a lower protocol layer. An SDU in turncan be understood as a data unit that is passed to/from a higherprotocol layer. Hence, for example what is a PDU to RLC is an SDU toMAC. Carrier aggregation (CA) can be used to increase performance. Incarrier aggregation a plurality of carriers are aggregated to increasebandwidth. Carrier aggregation comprises aggregating a plurality ofcomponent carriers into a carrier that is referred to in thisspecification as an aggregated carrier. For example, Release 10 (Rel-10)of the E-UTRA specifications introduces carrier aggregation (CA), wheretwo or more component carriers (CCs) are aggregated in order to supportwider transmission bandwidths. In CA it is possible to configure acommunication device to aggregate a different number of CCs originatingfrom the same eNodeB (eNB) and of possibly different bandwidths in theuplink (UL) and/or downlink (DL). In this regard a reference is made toFIG. 4 which shows five component carriers which have been aggregated.Each component carrier is 20 MHz in this example, giving an aggregatedbandwidth of 100 MHz.

When CA is configured, the communication device, for example an userequipment (UE) only has one radio resource control (RRC) connection withthe network. At radio resource control (RRC) connectionestablishment/re-establishment/handover, one serving cell provides thenon access stratum (NAS) protocol mobility information (e.g. TAI;tracking area identity) and at RRC connection re-establishment/handover,one serving cell provides the security input. The security input may beone ECGI (E-UTRAN cell global identifier), one PCI (physical cellidentifier and one ARFCN (absolute radio frequency channel number). Thisserving cell is referred to as the Primary Cell (PCell). In thedownlink, the carrier corresponding to the PCell is the Downlink PrimaryComponent Carrier (DL PCC) while in the uplink it is the Uplink PrimaryComponent Carrier (UL PCC). Depending on UE capabilities, SecondaryCells (SCells) can be configured to form together with the PCell a setof serving cells. In the downlink, the carrier corresponding to an SCellis a Downlink Secondary Component Carrier (DL SCC) while in the uplinkit is an Uplink Secondary Component Carrier (UL SCC).

The configured set of serving cells for a UE therefore can consist ofone PCell and one or more SCells. In is noted that 3GPP Release 8terminals/user equipments are assumed to be served by one serving cell,while LTE-Advanced capable terminals/user equipments can receive ortransmit simultaneously on multiple serving cells.

A handover procedure can be used despite the introduction of carrieraggregation. Regardless of whether the target cell belongs to theconfigured set of serving cells, a handover is used i.e. a procedurewhere MAC (media access control), RLC (radio link control) and PDCP(packet data convergence protocol) are reset, security keys are updatedand a random access procedure is performed in the target cell. When MACis reset HARQ transmission of MAC service data units (SDUs) receivedfrom radio link control (RLC) is interrupted. This occurs despitepossible HARQ NACKs that have been received from the peer node i.e. thereceiving MAC entity. Also, HARQ reception of MAC SDUs to be deliveredto the RLC layer is interrupted. This occurs despite any possible HARQNACKs that have been transmitted concerning failed reception of dataunits. When nothing is indicated to the RLC about the interruption andthe RLC is not reset, a RLC-internal mechanism needs to detect thelosses of such MAC SDUs, i.e. loss of the relevant RLC PDUs. Anacknowledged mode (AM) RLC entity then needs to initiate sending NACKsand retransmission. In the case of unacknowledged mode (UM), anunacknowledged mode (UM) RLC entity needs to deliver received SDUs toupper layer despite the lost PDUs. These steps can cause unnecessarydelay.

The current RLC-protocol specifications define that a receiving RLCentity shall use a reordering-timer (e.g. 36 in FIG. 2) to infer that aPDU that was not received amid other PDUs is no longer under HARQprocessing at the MAC layer but has actually gone missing. When thereordering-timer expires, the value of a state variable is updated: forRLC-AM the maximum status transmit state variable VR(MS) keeps record ofthe lowest RLC-PDU sequence number for which neither a positive nor anegative acknowledgement (because of possible HARQ processing stillunderway) can yet be confidently sent. For RLC-UM, UM receive statevariable VR(UR) holds the value of the sequence number (SN) of theearliest UMD PDU that is still considered for reordering.

The embodiments described below relate to optimisation of handling ofinterruptions within a device when one but not all protocol layers areinterrupted, for example when RLC functions are maintained while MAC isreset. The embodiments can be applied to reception where determining isprovided when non-received packets can be NACKed or overlooked atdelivery of other packets to higher layer. An indication of theinterruption of a first protocol can be given internally to a controlfunction entity of a second protocol still running at the receivingnode.

In accordance with an embodiment illustrated by the flowchart of FIG. 5reception of data units is handled at 50 based on a first protocol and asecond protocol, and more particularly by means of MAC and RLC entitiesof a device. An interruption of a control function of the first protocolmay be determined. For example, an RRC command by eNB can be received at51 by a user equipment, the command indicating explicitly that only aMAC function of the user equipment shall be reset. Based on the RRCcommand the MAC is then reset and a RLC function residing at the userequipment is informed of the reset at 52. An indication of the MAC resetmay be provided for each receiving RLC entity. At 53, subsequent ofbecoming aware of the MAC reset, the relevant RLC entity considers thereordering timer as having expired. Depending on the mode (UM or AM) anappropriate state variable is updated at 54 to equal with the highestreceived state variable.

It is noted that one or more of these steps may be performed under thecontrol of one or more processors in association with one or morememories. The steps may be the result of one or more computerinstructions being executed by one or more processors.

Certain more detailed examples are given below in relation tooptimization of operation when MAC is reset while RLC is not reset. Inaccordance with an embodiment an improved status reporting mechanism fordata transmissions between the peers (e.g. UE and eNB) in LTE networksis provided. A RLC entity of a node can decide immediately whether a RLCPDU needs to be retransmitted on higher layers (RLC ARQ). In evaluatingthe situation a decision algorithm can take into account the state ofthe MAC entity.

As mentioned above, an interruption can be caused by reset of a MACentity. This may be triggered by a reset command, e.g. a lighterhandover command from eNB, received on RRC layer of the UE. Only the MACcan be reset whereas higher layers like RLC and PDCP are not necessarilyimpacted by the reset command. The RRC layer can then instruct MAC toreset. If the MAC entity is reset based on reset command a decisionalgorithm can form a status report for the peer node immediately afterthe reset command is received by the MAC entity, and negativeacknowledgement of RLC PDUs determined to be missing based on the lateststatus is sent. In RLC UM-mode, data packets which are correctlyreceived are forwarded to the higher layers, whereas in RLC AM-mode datapackets which have not been received correctly before the reset occursare indicated for retransmission by RLC ARQ. The status report can besent to the peer node after the MAC reset. By providing NACKs for RLCPDUs whose transmission has been interrupted rather than waiting for thereordering timer to expire it is possible to carry out more speedily RLCPDU retransmissions once the MAC has been reset.

In case of RLC-AM the operation can be such that if the reordering-timeris running, a relevant RLC entity can consider the timer to expire inresponse to the RRC entity of the UE informing the RLC layer about MACreset. According to a possibility an indication of the reset is receivedfrom the MAC layer. The RLC entity can then update the maximum statustransmit state variable VR(MS) to that of the present value of thehighest received state variable VR(H). It is noted that if thereordering timer was not running, VR(MS) already equals VR(H).

The indication can also trigger status reporting. This reporting may beper the current specifications.

Triggering based on indication of reset rather than waiting for theexpiry of the reordering timer can mean that an acknowledgement(positive or negative) can confidently be sent for all received PDUs upto and including the one with highest sequence number in the receivingwindow.

It is also possible, when the reordering timer is considered to expireas a result of determining a MAC reset, to stop and reset a statusprohibit timer (e.g. timer 38 of FIG. 2) if such is running. This can beused to allow for immediate status reporting.

In accordance with an embodiment the reordering-timer is considered toexpire even if it is not running. A consequence of this is that statusreporting will become triggered in any case.

It is noted that in addition to retransmissions, similar principles canbe applied to other actions as well, for example UM actions. In RLC-UMcase, if the reordering timer is running, the RLC entity considers thetimer to expire in response to an indication of MAC reset and thereafterupdates the UM receive state variable VR(UR) to that of the presentvalue of UM highest received state variable VR(UH). If the reorderingtimer was not running, VR(UR) would be VR(UH) already. This means thatfor all received PDUs up to and including the one with highest sequencenumber in the reordering window, the contained SDUs can be delivered toupper layer without violating in-order delivery.

Information of MAC reset can thus be used to provide a mechanism toindicate between protocol layers that no further MAC SDUs can beexpected to finish ongoing HARQ retransmissions and then be delivered tothe RLC entity. If a missing RLC PDU was being expected for reception,this will trigger sending an RLC status PDU to the peer RLC after thereset (RLC-AM) or delivering all SDUs received thus far to upper layer(RLC-UM), without unnecessary delay.

A more detailed example of RLC actions taken when reordering timer(t-Reordering in LIE) expires are presented in the following for UM andAM scenarios.

A receiving UM RLC entity shall, when an indication of reset of lowerlayer is received and if t-Reordering is running, determine t-Reorderingto expire at this stage. When t-Reordering expires, the receiving UM RLCentity shall, if the expiry was due to an indication of reset of lowerlayer, set VR(UR) to VR(UH). If the expiry was not due to an resetindication, the receiving UM RLC shall update VR(UR) to the SN of thefirst UMD PDU with SN>=VR(UX) that has not been received. Other actionstaken in response to the expiry can include reassembly of RLC SDUs fromany UMD PDUs with SN<updated VR(UR), removal of RLC headers when doingso, and delivery of the reassembled RLC SDUs to an upper layer inascending order of the RLC SN if not already delivered. Also, ifVR(UH)>VR(UR) t-reordering can be started, and VR(UX) set to VR(UH).

In accordance with current RLC-AM, a Status-prohibit timer (e.g. timer38 in FIG. 2) is used to prevent sending RLC Status PDUs (carrying theRLC ACK/NACKs) too frequently. This timer can be started every time aStatus PDU is sent, and sending of another Status PDU is allowed onlywhen this timer expires. In accordance with an embodiment a receiving AMRLC entity shall, when an indication of reset of a lower layer isreceived and if the re-ordering timer is running determine ift-StatusProhibit is also running, and if so, stop and resett-StatusProhibit, and thereafter consider that the re-ordering timer hasexpired. When t-Reordering expires, the receiving side of an AM RLC pairshall, if the expiry was due to an indication of reset of lower layer,set VR(MS) to VR(H). Otherwise, the receiving AM RLC entity shall updateVR(MS) to the SN of the first AMD PDU with SN>=VR(X) for which not allbyte segments have been received. If VR(H)>VR(MS), t-Reordering shall bestarted and VR(X) set to VR(H). Reset indications to RLC entities may begiven from MAC or RRC layer. The indication can be delivered only whenMAC only is reset without a need to reset e.g. RLC. Thus, in accordancewith some embodiments if MAC is reset at the same time as e.g. the RLC,then no indications are delivered, or such indications may be ignored.

When MAC is reset without an RLC reset, the RLC layer can take intoaccount that HARQ protocol in MAC layer has been reset and that no moreHARQ retransmissions are possible. This enables RLC to make fasterdecisions about retransmissions (e.g. faster re-transmission of RLCPDUs), polling and delivery to higher layers. By means of this,reduction in service disruption during handovers where the eNBarchitecture does not reset the RLC may be achieved.

The embodiments may allow for reduction of processing time of intra-cellhandovers. For example, in LTE networks intra-cell handover has to betriggered whenever synchronous procedures have to be performed in eNBand user equipment (UE) to align to each other and when the UE does notchange the serving cell. When MAC is reset but RLC is not, immediateconfirmation that PDUs have gone missing may be given to RLC layer.

Intra-eNB handovers may become particularly important form of handoversin association with baseband pooling architectures. Scenarios wherebaseband pooling architectures such as for example liquid radio isdeployed a handover is always used regardless of whether the target cellbelongs to the same hardware pool as the source cell or not. Liquidradio is an example of technology that adapts the capacity and coverageof networks to match fluctuating user demand. The radio frequencyelements and the antenna become active, sized and positioned accordingto need while baseband processing is pooled and sited remotely. Basebandpooling centralizes the digital signal processing typically done at basestation sites and shares it with several sites to ensure that capacityis dynamically used where needed. This enables the network to match theactual capacity needs of end users as they change during the day or overlonger periods.

The required data processing apparatus and functions of a base stationapparatus, a communication device and any other appropriate apparatusmay be provided by means of one or more data processors. The describedfunctions at each end may be provided by separate processors or by anintegrated processor. The data processors may be of any type suitable tothe local technical environment, and may include one or more of generalpurpose computers, special purpose computers, microprocessors, digitalsignal processors (DSPs), application specific integrated circuits(ASIC), gate level circuits and processors based on multi core processorarchitecture, as non limiting examples. The data processing may bedistributed across several data processing modules. A data processor maybe provided by means of, for example, at least one chip. Appropriatememory capacity can also be provided in the relevant devices. The memoryor memories may be of any type suitable to the local technicalenvironment and may be implemented using any suitable data storagetechnology, such as semiconductor based memory devices, magnetic memorydevices and systems, optical memory devices and systems, fixed memoryand removable memory.

In general, the various embodiments may be implemented in hardware orspecial purpose circuits, software, logic or any combination thereof.Some aspects of the invention may be implemented in hardware, whileother aspects may be implemented in firmware or software which may beexecuted by a controller, microprocessor or other computing device,although the invention is not limited thereto. While various aspects ofthe invention may be illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it is wellunderstood that these blocks, apparatus, systems, techniques or methodsdescribed herein may be implemented in, as non-limiting examples,hardware, software, firmware, special purpose circuits or logic, generalpurpose hardware or controller or other computing devices, or somecombination thereof. The software may be stored on such physical mediaas memory chips, or memory blocks implemented within the processor,magnetic media such as hard disk or floppy disks, and optical media suchas for example DVD and the data variants thereof, CD.

It is noted that whilst embodiments have been described in relation toLTE-Advanced, similar principles can be applied to any othercommunication system or indeed to further developments with LTE.Embodiments may be used where there is carrier aggregation in scenariosother than the LTE situations described above. Alternatively oradditionally, embodiments may be used where a simplified handoverprocedure may be used. For example, the invention is applicable forcarrier or cell aggregation even when coordinated multipoint (CoMP) isnot supported, for example to multi-flow in standards such as High SpeedPacket Access (HSPA). Also, instead of carriers provided by a basestation a carrier may be provided by a communication device such as amobile user equipment. For example, this may be the case in applicationwhere no fixed equipment provided but a communication system is providedby means of a plurality of user equipment, for example in adhocnetworks. Therefore, although certain embodiments were described aboveby way of example with reference to certain exemplifying architecturesfor wireless networks, technologies and standards, embodiments may beapplied to any other suitable forms of communication systems than thoseillustrated and described herein. It is also noted that the hereindescribed embodiments may also be used for scenarios such asintra-frequency serving cell change.

The foregoing description has provided by way of non-limiting examples afull and informative description of certain embodiments of theinvention. However, various modifications and adaptations may becomeapparent to those skilled in the relevant arts in view of the foregoingdescription, when read in conjunction with the accompanying drawings andthe appended claims. However, all such and similar modifications of theteachings of this invention will still fall within the scope of thisinvention as defined in the appended claims. Indeed there is a furtherembodiment comprising a combination of one or more of any of the otherembodiments previously discussed.

The invention claimed is:
 1. A method comprising: receiving, by acontrol function of a second protocol of a receiving device, informationfrom the receiving device about an interruption in a control function ofa first protocol of the receiving device, said second protocol being ahigher layer in a hierarchical order of protocol layers than said firstprotocol; in response to receiving said information, stopping areordering timer of the second protocol of the receiving device, whenthe reordering timer is running; and in response to receiving saidinformation, updating a state variable, other than a highest receivedstate variable, of the second protocol of the receiving device to equalthe highest received state variable of the second protocol of thereceiving device, wherein the second protocol is located above the MACprotocol in the layered protocol model, and wherein the second protocolis radio link control (RLC) protocol or packet data convergence protocol(PDCP).
 2. The method as claimed in claim 1, wherein the interruptioncomprises a reset of the control function of the first protocol at areceiving node.
 3. The method as claimed in claim 1, wherein the firstprotocol comprises media access control (MAC) protocol.
 4. The method asclaimed in claim 1, wherein the first protocol is medium access control(MAC) protocol and the control function thereof provides hybridautomatic repeat request (HARQ) functionalities.
 5. The method asclaimed in claim 1, further comprising: using a higher level protocolmechanism for retransmission of the data units than MAC HARQ.
 6. Themethod as claimed in claim 1, wherein said information of theinterruption is received from a media access control (MAC) protocol orradio resource control RRC protocol entity.
 7. The method as claimed inclaim 1, wherein the update comprises update of a maximum statustransmit state variable to equal the highest received state variable. 8.The method as claimed in claim 1, wherein the information triggersupdate of an unacknowledged mode received state variable to equal anunacknowledged mode highest received state variable.
 9. The method asclaimed in claim 1, further comprising: stopping and resetting a statusprohibit timer in response to stopping the reordering timer.
 10. Themethod as claimed in claim 1, further comprising: determining, inresponse to said information of the interruption, that no furtherretransmissions of protocol data units transmitted so far in accordancewith the first protocol can be expected; and in response thereto,sending a status protocol data unit in accordance with the secondprotocol and/or delivering so far received service data units to anupper protocol layer.
 11. The method as claimed in claim 1, wherein themethod is performed during intra-cell handover.
 12. An apparatuscomprising: at least one processor; and at least one memory includingcomputer program code, wherein the at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus at least to: receive, by a control function of a secondprotocol of the apparatus, information from the apparatus about aninterruption in a control function of a first protocol of the apparatus,said second protocol being a higher layer in a hierarchical order ofprotocol layers than said first protocol; in response to receiving saidinformation, stop a reordering timer of the second protocol of theapparatus, when the reordering timer is running; and in response toreceiving said information, update a state variable, other than ahighest received state variable, of the second protocol of the apparatusto equal the highest received state variable of the second protocol ofthe apparatus, wherein the second protocol is located above the MACprotocol in the layered protocol model, and wherein the second protocolis radio link control (RLC) protocol or packet data convergence protocol(PDCP).
 13. The apparatus as claimed in claim 12, wherein theinterruption comprises a reset of the control function of the firstprotocol at a receiving node.
 14. The apparatus as claimed in claim 12,wherein the first protocol comprises media access control (MAC)protocol.
 15. The apparatus as claimed in claim 12, wherein the controlfunction of the first protocol is adapted to provide hybrid automaticrepeat request (HARQ) functionalities.
 16. The apparatus as claimed inclaim 12, wherein the at least one memory and the computer program codeare further configured, with the at least one processor, to: update amaximum status transmit state variable to equal the highest receivedstate variable.
 17. The apparatus as claimed in claim 12, wherein the atleast one memory and the computer program code are further configured,with the at least one processor, to: update an unacknowledged modereceived state variable to equal an unacknowledged mode highest receivedstate variable in response to the information.
 18. The apparatus asclaimed in claim 12, further comprising: a status prohibit timer,wherein the apparatus is configured to stop and reset the statusprohibit timer in response to stopping the reordering timer.
 19. Theapparatus as claimed in claim 12, wherein the at least one memory andthe computer program code are further configured, with the at least oneprocessor, to: determine, in response to said indication, that nofurther retransmissions of protocol data units transmitted so far inaccordance with the first protocol can be expected; and in responsethereto, cause sending of a status protocol data unit in accordance withthe second protocol and/or delivery of so far received service dataunits to an upper protocol layer.
 20. The apparatus as claimed in claim12, wherein the apparatus is configured to handle reception of dataunits during intra-cell handover.
 21. A communication device comprisingthe apparatus in accordance with claim
 12. 22. A computer programproduct comprising a non-transitory computer readable storage mediumbearing computer program code embodied therein for a computer, thecomputer program code comprising code for performing the following:receiving, by a control function of a second protocol of the receivingdevice, information from the receiving device about an interruption in acontrol function of a first protocol of the receiving device, saidsecond protocol being a higher layer in a hierarchical order of protocollayers than said first protocol; in response to receiving saidinformation, stopping a reordering timer of the second protocol of thereceiving device, when the reordering timer is running; and in responseto receiving said information, updating a state variable, other than ahighest received state variable, of the second protocol of the receivingdevice to equal the highest received state variable of the secondprotocol of the receiving device, wherein the second protocol is locatedabove the MAC protocol in the layered protocol model, and wherein thesecond protocol is radio link control (RLC) protocol or packet dataconvergence protocol (PDCP).